CDK16 overexpressed in non-small cell lung cancer and regulates cancer cell growth and apoptosis via a p27-dependent mechanism

Cyclin-dependent kinase 16 (CDK16, PCTAIRE1) expression is upregulated in a wide variety of human malignancies. However, the function(s) of CDK16 in non-small cell lung cancer (NSCLC) remain unknown. Therefore, here we investigated the role of CDK16 in NSCLC. From 43 NSCLC tumors and matching healthy control lung tissues, immunohistochemistry revealed significantly greater CDK16 and phospho-p27^Ser10 staining levels in NSCLC samples relative to healthy controls. The NSCLC cell line EKVX was transfected with a control siRNA, a CDK16-siRNA, or CDK16-siRNA + p27-siRNA. We found significantly decreased proliferation levels and significantly increased apoptosis levels in CDK16-silenced NSCLC cells. However, these effects were abrogated in cells treated with both the CDK16-siRNA and the p27-siRNA. In CDK16-silenced NSCLC cells, we found upregulated p27 and downregulated phospho-p27^Ser10 protein expression but downregulated ubiquitinated p27 and ubiquitinated phospho-p27^Ser10 protein expression. Cycloheximide-treated CDK16-silenced NSCLC cells displayed a much milder reduction in p27 protein expression over time relative to untreated CDK16-silenced NSCLC cells. In summary, CDK16 is significantly upregulated in human NSCLC tumor tissue and plays an oncogenic role in NSCLC cells via promoting cell proliferation and inhibiting apoptosis in a p27-dependent manner. Moreover, CDK16 negatively regulates expression of the p27 via ubiquination and protein degradation.

Gene methylation in gastric cancer

Gastric cancer is one of the most common malignancies and remains the second leading cause of cancer-related death worldwide. Over 70% of new cases and deaths occur in developing countries. In the early years of the molecular biology revolution, cancer research mainly focuses on genetic alterations, including gastric cancer. Epigenetic mechanisms are essential for normal development and maintenance of tissue-specific gene expression patterns in mammals. Disruption of epigenetic processes can lead to altered gene function and malignant cellular transformation. Recent advancements in the rapidly evolving field of cancer epigenetics have shown extensive reprogramming of every component of the epigenetic machinery in cancer, including DNA methylation, histone modifications, nucleosome positioning, noncoding RNAs, and microRNAs. Aberrant DNA methylation in the promoter regions of gene, which leads to inactivation of tumor suppressor and other cancer-related genes in cancer cells, is the most well-defined epigenetic hallmark in gastric cancer. The advantages of gene methylation as a target for detection and diagnosis of cancer in biopsy specimens and non-invasive body fluids such as serum and gastric washes have led to many studies of application in gastric cancer. This review focuses on the most common and important phenomenon of epigenetics, DNA methylation, in gastric cancer and illustrates the impact epigenetics has had on this field.